Search for a key in a nested Python dictionary

E

2

6

I have some Python dictionaries like this:

A = {id: {idnumber: condition},....

e.g.

A = {1: {11 : 567.54}, 2: {14 : 123.13}, .....

I need to search if the dictionary has any idnumber == 11 and calculate something with the condition. But if in the entire dictionary doesn't have any idnumber == 11, I need to continue with the next dictionary.

This is my try:

for id, idnumber in A.iteritems():
    if 11 in idnumber.keys(): 
       calculate = ......
    else:
       break

Eadith answered 6/10, 2011 at 22:42 Comment(1)

see also: #14693190 – Significant 12/7, 2018 at 20:53

B

7

You're close.

idnum = 11
# The loop and 'if' are good
# You just had the 'break' in the wrong place
for id, idnumber in A.iteritems():
    if idnum in idnumber.keys(): # you can skip '.keys()', it's the default
       calculate = some_function_of(idnumber[idnum])
       break # if we find it we're done looking - leave the loop
    # otherwise we continue to the next dictionary
else:
    # this is the for loop's 'else' clause
    # if we don't find it at all, we end up here
    # because we never broke out of the loop
    calculate = your_default_value
    # or whatever you want to do if you don't find it

If you need to know how many 11s there are as keys in the inner dicts, you can:

idnum = 11
print sum(idnum in idnumber for idnumber in A.itervalues())

This works because a key can only be in each dict once so you just have to test if the key exits. in returns True or False which are equal to 1 and 0, so the sum is the number of occurences of idnum.

Ballerina answered 6/10, 2011 at 22:46 Comment(4)

hi @Ballerina thanks for your help. btw, what should I do if I want to count the number of 11 in idnumber?? THANKS!!! :) – Eadith 7/10, 2011 at 2:7

I'm not sure of your question? idnumber is a dict, and idnum is a key in that dict, so there can only be one idnum in each idnumber. If you mean the total number of idnumber dicts that have 11s as keys I'll add it to my answer. – Ballerina 7/10, 2011 at 2:19

sorry, I didn't explain correctly. those dictionaries are in a way that id is like a counting for each idnumber, i.e. like this {1: {15: 67.4}, 2: {13: 78.4}, 3: {11 : 723.73}, 4: {11 : 34.21}... so I need to count how many 11 are in all idnumbers in each dict. Thanks for your time!!! :) – Eadith 7/10, 2011 at 3:11

@Eadith That's what the code I added to the bottom of my answer does. – Ballerina 7/10, 2011 at 3:18

T

8

dpath to the rescue.

http://github.com/akesterson/dpath-python

dpath lets you search by globs, which will get you what you want.

$ easy_install dpath
>>> for (path, value) in dpath.util.search(MY_DICT, '*/11', yielded=True):
>>> ... # 'value' will contain your condition; now do something with it.

It will iterate out all of the conditions in the dictionary, so no special looping constructs required.

idnum = 11
# The loop and 'if' are good
# You just had the 'break' in the wrong place
for id, idnumber in A.iteritems():
    if idnum in idnumber.keys(): # you can skip '.keys()', it's the default
       calculate = some_function_of(idnumber[idnum])
       break # if we find it we're done looking - leave the loop
    # otherwise we continue to the next dictionary
else:
    # this is the for loop's 'else' clause
    # if we don't find it at all, we end up here
    # because we never broke out of the loop
    calculate = your_default_value
    # or whatever you want to do if you don't find it